This invention relates to shuttle cleaning of heat exchanger tubes and is an improvement over the concepts disclosed in the above-identified patents.
It is known from the above-identified patents to connect individual elongated cleaning element capturing cages or baskets to both ends of longitudinally extending tubes disposed in a heat exchanger housing. The tube ends are held in position at both ends by transverse tube sheets. The baskets are adapted to contain shuttlable cleaning elements, such as brushes. Fluid flowing in one direction through the tubes keeps the cleaning elements captured within their respective basket chambers, while the fluid discharged outwardly through slot-like openings in the basket walls. Upon reversal of fluid flow, the cleaning elements are forced out of their baskets and through the tubes to the baskets at the opposite tube ends to thereby perform a tube cleaning action.
Reference is made to the present inventors' co-pending U.S. patent application Ser. No. 350,286, filed on even data herewith and entitled "Basket Retainer For Heat Exchanger Tube Cleaning Element". In that application, a basket retaining plate is fixedly mounted, as by bolts or the like, in spaced relationship outwardly from the outer tube sheet face. The plate and its mount cooperate with the tube sheet to hold the baskets in fixed position relative to the tube sheet and tube ends. The outer capturing and holding portions of the baskets extend outwardly from the retaining plate. The baskets include central or intermediate portions which extend through openings in the plate and inner portions which extend through the space between the plate and tube sheet and which terminate within the tube sheet. The baskets are fixedly secured against transverse shifting by a two-point support, one at the inner basket ends and one intermediate their ends. To hold the baskets in longitudinally fixed position, and in one embodiment, the basket intermediate portions are threaded to the retaining plate. In another embodiment, shoulders adjacent the inner basket ends engage the plate and tube sheet. The retaining plate is of lesser diameter than the tube sheet and is provided with unobstructed fluid flow openings between the baskets and basket-receiving openings.
In some instances, as where there is little space available between the retaining plate and the heat exchanger head end or when only short baskets are desired, it is not feasible to dispose the baskets longitudinally outwardly of the retaining plate as is shown in the aforementioned application.
It is a task of the present invention to provide the advantages of the retaining plate even when the baskets do not extent outwardly thereof.
In accordance with the various aspects of the invention, the baskets are positioned so that their basket holding chambers having fluid flow openings in the side walls thereof are disposd in the space between the retaining plate and tube sheet. The outer end portions of the baskets are engaged by the retaining plate while the inner end portions of the baskets are positioned relative to the tube sheet openings to be in fluid communication with the heat exchanger tubes. The retaining plate has a plurality of openings therein which may be in axial alignment with the tube sheet openings and in axial registry with the open outer ends of the axial baskets. Alternately, the retaining plate openings may be arranged in a random pattern basically out of alignment with the tube sheet openings and out of registry with the baskts. The total cross-sectional area of the random openings in a retainer plate is preferably equal to or greater than the sum of the internal cross-sectional areas of the heat exchanger tubes.